Production of primary alkylaromatics from secondary and tertiary alkylaromatics



United States Patent No Drawing. Filed June '25, 1959, Ser. No. 822,7297 Claims. (Cl. 260668) This invention relates to the selective catalyticisomerization of substituted aromatics having at least one side chain ofalkyl character attached through a secondary or tertiary alkyl carbonatom to produce an isomer having the side chain attached through aprimary alkyl carbon atom.

While certain of the lower alkylaromatic hydrocarbons such as tolueneand xylene may be recovered from cracked petroleum fractions, coal tarproducts, and the like, those containing side chains having 3 or morecarbon atoms are generally too costly to separate and are normallyprepared by alkylating a suitable aromatic hydrocarbon, e.g., benzene,xylene, naphthalene, or the like, with an appropriate olefinic material.In such alkylation the point of attachment of the side group is througha tertiary carbon atom or through a secondary carbon atom, but notthrough a primary carbon atom. Thus, alkylation with propylene yieldsthe isopropyl derivatives (secondary carbon attachment), butene-l andbutene-Z give the secondary butyl derivatives, and isobutylene yieldsthe tertiary butyl derivatives. The corresponding normal derivatives,i.e. attached through a primary carbon atom, are not formed.

While the substituted aromatic hydrocarbons having the side groupattached through a secondary or tertiary carbon atom are thereforereadily prepared and available for commercial use, those having groupsof 3 or more carbon atoms attached through a primary carbon atom requirea much more involved synthesis. While these latter may be purchased asfine chemicals for research at a cost of several dollars per pound theyhave not been, up to the present, available in quantities and at a costconducive to commercial use.

It is known that alkylaromatics can be isomerized with various Lewisacid type catalysts such, for example, as AlCl FeCl P 0 HF-BF and thelike. This isomerization generally takes place at relatively lowtemperatures. However, even at relatively low temperatures theisomerization is accompanied by disproportionation and usually byappreciable cracking and degradation to tars and the like.

The primary isomerization with acid catalysts and when at least twoalkyl groups are present involves a shift of thealkyl side chainstowards equilibrium between the position isomers, i.e. the ortho, metaand para isomers. (See Norris, J. F. and Vaala, G. T. Ind. Eng. Chem.,61, 2l31-2l34 (1939).)

Disproportionation also takes place to a considerable extent and in twoways. Firstly, there is considerable shift of groups from one aromaticring to another or; in effect, dealkylation of some molecules withfurther alkylation of others. Thus, for example, the isomerization ofxylenes leads to the formation of benzene, toluene,

2 and higher boiling polymethylated benzenes in addition to the positionisomers. (See Baddeley, G. and Kenner, 1., J. Chem. Soc., 303 (1935).)

The other or second type of disproportionation reac= tion occurs betweenalkyl groups and is exemplified by the conversion of xylene toethylbenzene. This type of disproportionation becomes of importance whenusing certain types of isomerization catalysts. (See Holzmari, 'G. andGood, US. 2,656,397.)

In a few cases where a normal C side chain is present in the initialmaterial subjected to an isomerization treatment with AlCl it has beenreported that the side chain may simultaneously isomerize to an iso sidechain while changing position on the aromatic nucleus. Thus,l-npropyl-Z,4-dimethylbenzene has been reported to isomerize to1,3-dimethy1-S-isopropylbenzene. (See Nightengale, D, and Carton In, B.,J. Am. Chem. Soc., 62, 280-283 (1940).) This is, however, quitediiferent than the isomerization sought and obtained by the presentinvention. Moreover, there is some question as to whether or not suchisomerization actually takes place. (See Condon, F. E. in Catalysis VI,Emmett, C. H., p. 107 New York, Reinhold Publishing Company (1958).)

Thus, side chains attached through a primary carbon atom migrate on thearomatic nucleus but isomerization from a secondary side chain to anormal side chain or of a tertiary side chain to an iso side chainclearly does not take place. (See McCaulay, D. A., and Lien, A. D., J.Am. Chem. Soc, 75, 2411 (1953).)

The experimentally observed isomerizations of alkylaromatics mentionedabove have quite conclusively been shown to take place by a carboniumion mechanism. On the basis of the carbonium ion theory, and in keepingwith the experimentally determined results, we would not expect to beable to convert an alkylaromatic having a secondary or tertiary sidechain into an isomer having the corresponding normal or iso side chainby a carboniurn mechanism.

If an alkylaromatic is treated under drastic conditions without anycatalyst, i.e. thermally at cracking or incipient cracking temperatures,a small amount of isomerization from a secondary alkyl group to aprimary alkyl group takes place. (See Ipatieff, V. N., Pines, H., andKvetinskas, B., US. Patent No. 2,671,120.) However, this requires theuse of very high pressures. Also the reaction is accompanied by crackingand other side reactions. Thus, in the case of isopropylbenzene (themost stable of the alkyl aromatics under consideration) at 3000 p.s.i.g.and 475 C. no reaction takes place: at 12,000 p.s.i.g. and 479 C. about22% of the isopropylbenzene is reacted giving 12.7% ofnormal-propylbenzene at 9.3% of cracked products: at 12,000 p.s.i.g. and501 C. 44.5% of the isopropylbenzene is reacted giving 14.8%normal-propylbenzene and 29.7% of cracked products.

We have now discovered that by employing different and selectedconditions whereby a catalytic free radical mechanism controls it isindeed possible for the first time to catalytically isomerize aromatichydrocarbons having one or more groups attached through a secondary ortertiary alkyl carbon atom to the corresponding isomer having the groupattached through a primary carbon atom. Thus, it is now possible toisomerize tertiary groups to iso groups and secondary groups to normalgroups. Moreover it is found that the isomerization can be made quiteselective, i.e. to take place without migration of the groups and withlittle cracking, dehydrogenation, polymerization, or other sidereactions. Good yields may therefore be obtained and the process for thefirst time allows the desirable primary isomers to be produced from thesecondary and tertiary isomers at a cost which is not prohibitive forcommercial application.

It may be noted that it has been indicated that the neophyl radical iscapable of rearrangement to give some of the corresponding isobutylgrouping. (See Kharasch. M. S., and Urry, W. H., J. Am. Chem. Soc., 66,1438 (1944) and Winstein, S., and Seubold, F., J. Am. Chem. Soc., 69,2916 (1947).) This work, however, did not involve isomerization of analkylaromatic hydrocarbon and it involved a stoichiometric rather than acatalytic method. In the first case, 1-chloro-2-methyl-2-phenylpropanereacted with a stoichiometric quantity of a Grignard reagent in thepresence of cobaltous chloride catalyst. In the second case astoichiometric amount of 3,3-dimethyl-3-phenylpropionaldehyde wasdecomposed with a peroxide. The mechanism postulated to explain themixture of products obtained involved rearrangement of the neophylradical as stated above.

The process of the invention is applicable for the isomerization ofmononuclear and polynuclear aromatics, as hereinafter defined, having atleast one hydrogen atom substituted by a side group which is essentiallya hydro carbon group containing at least three carbon atoms of which atleast two and preferably not more than five are alkyl carbon atoms, saidgroup being attached to the aromatic nucleus through a secondary ortertiary carbon atom. This definition is intended to include true alltylgroups having three to five alkyl carbon atoms, e.g. the propyl group,and also alkyl groups having an aromatic substituent attached. Thus, thelowest member of the first type is cumene and the lowest member of thesecond type is 1,1-diphenyl ethane.

When the attached group is connected through a secondary alkyl carbonatom the isomer produced has the group attached through a primary carbonatom. When the attached group is connected through a tertiary carbonatom the isomer is also attached through a primary carbon atom but thegroup is normally of the iso configuration. An exception is the casewhere the alkyl group is a tertiary amyl group in which case theisomerization may be such that the attachment is shifted from thetertiary carbon atom to the secondary carbon atom as well as to one ofthe primary carbon atoms.

The side group is preferably free of ethylenic and acetylenicunsaturation because compounds containing side groups having suchunsaturation are generally quite prone to polymerization or undergoother side reactions under the reaction conditions. Compounds having anyindividual side groups having more than five connected alkyl carbonatoms are generally not suitable starting materials since the largenumber of non-profitable points of attack by free radicals favor sidereactions to an excessive extent. Thus, while aromatics having a highlybranched alkyl side chain up to around eight carbon atoms might beprofitably isomerized (depending upon economics) it is generallyrecommended to retain the maximum size of any individual alkyl group tonot more than six and preferably not more than five carbon atoms.

There may be only one side chain attached to the aromatic nucleus as forexample, isopropyl benzene which is the lowest member, or on the otherextreme, each of the hydrogens of a polycyclic aromatic may besubstituted by a side group, as above defined, up to the limit imposedby steric hindrance.

The groups attached to the aromatic nucleus may be the same ordifferent, provided that the largest alkyl group does not have more thanabout 5 carbon atoms. Thus, the alkylaromatic hydrocarbon may containany number of possible additional methyl, ethyl, phenylmethyl,phenylethyl, etc. side groups,

The isomerization is effected at temperatures between about 350 and 525C. and, in general, temperatures between about 400 and 475 C. arepreferable with most of the applicable catalysts. At temperatures belowabout 350 C. the isomerization is generally too slow to be practicablein commercial operation and at temperatures above about 525 C. thealkylaromatics are cracked and dehydrogenated to such an extent thatreasonable yields of the desired isomer are not obtained.

The isomerization may be effected with the alkylaromatic in the vaporphase, but good results may also be obtained when the alkylaromatic ismaintained largely, if not completely, in the liquid phase. Pressuresfrom atmospheric to 2000 p.s.i.g. have been successfully employed.Suggested pressures are from about 50 to about 1000 p.s.i.g.

The contact time to be used to obtain selective isomerization dependsupon the conditions and may range from about /2 minute to about 5 hours.The contact time in this case is the so-called nominal contact timecomputated from the molar input rate at the reaction temperature andpressure and considering the vapors to conform to the laws for perfectgases. The optimum con tact time is shorter the higher the temperatureand vice versa and depends somewhat on the catalyst used, the amount ofcatalyst used, and the particular all-zylbenzenc being isomerizcd. Whenoperating at the lowest possible temperature with the alkylaromatic inthe liquid phase contact times up to about 5 hours may be used orrequired. An important point to be observed is that the contact timeshould not be appreciably longer (with the feed, catalyst, andtemperature) than that necessary to achieve a reasonable approach to theequilibrium concentration ratio of the feed isomer to the productisomer. It is recommended to limit the contact time in any case suchthat the conversion to the desired isomer does not give a concentrationmore than 95% of that corresponding to the equilibrium concentrationunder the reaction conditions since it has been found that any longercontact time leads only to appreciable side reactions and loss of thedesired isomer.

Diluents which are substantially inert under the processing conditionsmay be included with the feed if this is desirable, e.g., to avoid anunnecessary step in separating them prior to isomerization. Forinstance, an aromatic hydrocarbon or mixture of aromatic hydrocarbonsmay be alkylated with an olefinic gaseous fraction of C -C hydrocarbonsobtained in the cracking of a petroleum oil in which case a mixture ofethyl, isopropyl, and tertiary-butyl alkylated aromatics is obtained;some of these are susceptible to isomerization according to theinvention and others are not. Such complicated mixtures may beisomerized but their use is not recommended. As another example, ahighly aromatic fraction obtained by the catalytic reforming of anaphthenic petroleum fraction and containing various aromatics as wellas paraffins and unconverted naphthenes may be alkylated with propyleneor butylene and the product then isomerizcd. This also, althoughpossible, generally involves complicated separation problems and is notrecommended where separation of a single isomer is the objective.Hydrogen, carbon dioxide, carbon monoxide, nitrogen, methane and similarinert gases may be present as diluents in most cases although theirpresence in appreciable amounts offers no advantage of consequence. Somematerials such as water (steam), alcohols, and other oxygenatedmaterials exert no harmful effects in small concentrations but may beharmful in concentrations above a few percent. Oxygen per se is notharmful in small amounts and in fact in many cases a small percentage ofelemental oxygen is beneficial.

As indicated above, the process of the invention is dependent uponselecting conditions conducive to a free radical chain reactionmechanism. This requires the use,

not only of the prescribed operating conditions but also, of a catalyticamount of a suitable catalyst capable of initiating and maintaining thefree radical reaction under the prevailing conditions. In principle, anycompound is applicable which under the operating conditions is capableof producing in catalytic amounts free radicals that reversibly abstracthydrogen atoms. Those skilled in the art of free radical reactions willrecognize this class of catalysts. (See, for example, Steacie, E. W. K.,Atomic and Free Radical Reactions, Reinhold Publishing Corpor-ation, NewYork (1954), and especially vol. I, pages 253-273.)

Excellent catalysts are the elements bromine, iodine, sulfur, seleniumand tellurium as such and in the form of their hydrides and semi-labileorganic compounds, e.g. the analogs of hydrocarbons, alcohols, ethers,ketones, aldehydes, acids, esters, amines, amides, nitriles and thelike. Of these materials those containing bromine are generally betterthan most of the others.

While the above-mentioned materials and others are operable in at leastsome cases it is not to be inferred that they are equivalent. Thecorresponding materials in which chlorine is substituted for one of theabove can also be used in many cases but are generally inferior. On theother hand, whereas bromine, iodine, hydrogen bromide and hydrogeniodide are excellent catalysts, chlorine reacts immediately with thehydrocarbon to form hydrogen chloride which is very stable under mostreaction conditions and is generally a poor catalyst. Similarly, whereassulfur and chloro-acetone are good catalysts, the bond to the sulfur orchlorine in such compounds as thiophene and chlorobenzene is so strongthat few free radicals are produced under the reaction conditions andhence the isomerization is catalyzed only to a small extent. In keepingwith the above rules, benzyl bromide is a better catalyst than iodine orisopropyl iodide; mercaptans and disulfides are for the same reasonsless effective than the iodides and bromides under comparableconditions.

In general, when using the sulfur, selenium or telluriumcontainingcatalysts, the concentration based on the catalytic element should besomewhat higher on a mole basis than when using catalysts containingbromide or iodine. However, if too large a concentration of sulfurcontaining catalyst, e.g. mercaptan and sulfides, is used, unsaturatedproducts such as alpha and beta-methylstyrene become important sidereaction products. This is particularly important when operating at lowconversion levels. On the other hand, in the isomerization of cumenewith isopropyl iodide as the catalyst, an increase of the iodineequivalent 1 from 1 mole percent to 5 mole percent affords an increasein the conversion from about 40% to about 60% with-f out materiallyaffecting the selectivity which was about reacts immediately, especiallyif light is present. It is, therefore, the resulting chloride whichactually acts as the catalyst. This is probably likewise the case atleast to some extent with bromine, iodine and sulfur.

Merely by way of comparison some materials that were tested and found tobe inoperative are a potassium promoted chromia-alumina catalyst withand without hydrogen present, Columbia activated carbon, aluminumchloride, various nickel sulfide catalysts having various atomic ratiosof nickel to sulfur.

The operable materials act as catalysts and not as reactants and areused only in catalytic amounts, e.g. 0.1 to 3 mole percent. In general,only a fraction of 1 mole percent of the catalyst, based on the feed, isrequired and in general it is preferred to employ concentrations not inexcess of about 3 mole percent; however concentrations as high as 10mole percent have been employed successfully in some cases. It will benoted that some of the applicable catalysts, and especially those inelemental form, are capable of reacting stoichiometrically and those, inparticular, should be used in only small concentrations, e.g., less than3 mole percent, to preserve the selective isomerization desired. In anycase as a criterion of catalytic operation the moles of isomer formedshould exceed by several fold the moles of catalyst used.

The catalyst is preferably mixed with the feed to be isomerized prior tocharging to the reaction zone, but it may, if desired, be chargedseparately to the reaction zone either at a single point or at multiplepoints. No particular advantage is seen, however, in the latter type ofoperation.

The reaction zone wherein the alkyl aromatic feed and catalyst arecontacted may be an empty reaction chamber with means for maintainingthe desired temperature, pressilre, and flow rate, or it may be packedwith a substantially inert foraminous solid material to improve thetransfer of heat. Obviously, from what has been shown above, no materialinducing carbonium ion isomerization to any appreciable extent should bepresent in the reaction zone since the presence of such materialdetracts materially from the efficiency and selectivity of theisomerization process. In general, the preferred reaction zone consistsof one or more cylindrical and vertically disposed chambers either emptyof solids or containing a relatively inert fixed bed or fluidized bed ofsolid material through which the material to be isomerized is passed,along with the catalyst, in a continuous manner. Since the isomerizationis for all practical purposes thermally neutral there is little to begained by the used of such W solid material. Batchwise processing in abomb type re- 70%. As thus indicated, it is preferable in seekinghigher" conversion in any particular case to vary the concentra'" tionof the catalyst in preference to unduly increasing the bromide; iodine,organic iodides exemplified by 2-iodo-" propane and iodobenzene; organicsulfur compounds exemplified by thiophenol, diphenyl disulfide, ethylmercaptan; organic chlorides exemplified by Z-chloropropane;

sulfur, and hydrogen sulfide.

Elemental chlorine is operative although it generally actor is alsopossible but less desirable for commercial operation.

The materials of which the reactor is constructed or lined dependsprimarily upon the choice of catalyst and the pressure. In many casesmild steel may be used; in other cases vessels constructed of orlinedlwith corrosion resistant material may be advisable or necessary.

The isomerized alkylaromatic containing the alkyl sid'e chain attachedthrough a primary carbon atom may in general be recovered from thereactor effluent in a simple manner. Generally, the eflluent may bewashed with water or an alkali to destroy or render harmless anycorrosive material, and then fractionally distilled to recover thedesired isomer. In some exceptional cases seperation by more elaboratetreatments, e.g., molecular sieve separation or solvent treatments, maybe more economical. The unconverted material may be recycled to v thereaction zone with fresh catalyst, or in some cases the bottoms from thedistillation contain sufiicient of the catalyst and may be also recycledin whole or in part.

The isomerized products obtainable by the method of the invention arechiefly of value as intermediates in the production of industrialchemicals. By way of example, the invention allows epoxidizedbeta-methylstyrenc, allylbenzene, diallylbenzene, and phenylbutadieneand many other desirable intermediates to be produced in a better andmore practicable manner. The epoxidized beta-methylstyrene is equallysuitable for applications where epoxidized styrene oralpha-methylstyrene have been used, e.g., as a cross linking agent inresinous polymers. One suggested synthesis of this material follows:Benzene is alkylated with propylene in the known manner. The resultingisopropylbenzene is separated from the product and isomerized tonormal-propylbenzene in accordance with the present process. Thenormal-propylbenzene is dehydrogenated by known methods to producebeta-methylstyrene which is then epoxidized in the manner that styreneis epoxidized. If para-diisopropylbenzene is recovered from thealkylation product and handled in the same manner the resulting epoxyproduct is an excellent resin monomer.

Allylbenzene may be prepared in a similar manner except that instead ofepoxidizing the beta-methylstyrene it is isomerized in a known manner byreacting with an alkyl boron compound followed by decompositionwhereupon the allylbenzone is produced.

Phenylbutadiene may be produced by alkylating benzene with butene-l orbutene-2 and isomerizing the re sulting secondary-butylbenzene asdescribed to produce the normal-butylbenzene. The normal-butyl sidechain may then be dehydrogenated to an olefinic side chain by reactingwith the stoiehiometric quantity of iodine and the resulting unsaturatedcompound can then be further de hydrogenated to the diene using themethods used for the dehydrogenation of butene-2 to butadiene.

The process of the invention will be illustrated by a number of exampleswhich will also indicate the effects of the conditions upon theconversion and selectivity.

EXAMPLE I A series of isomerizations of isopropylbenzene was Table IConvern-propyl Temp, C. Time, sion, Selectivity, benzene min. PercentPercent moles/100 moles teed Table II Gonvcn Selccu-prum-L CatalystTime, siou, tivity. 'ncnzcur min. Percent; Percent moles/100 moles fowlBenzyl bromide 10.5 41. 3 81 33. 5 Is0pr0py1iodide ca. 11 38. 9 T2. 623.2 ltenzyl br0mi(le.-.... 6. 0 30. 8 84. (i 31.1 Isopropyl chloride.10. 1 4. 7 2. 1 None .1 7.8 5.3 1.0

When the concentration of isopropyl iodide was increased to 10 molepercent, other conditions remaining the same, the conversion increasedto 60.5% but the selectivity declined to 66.4%.

When with 2 mole percent isopropyl iodide the pressure was increased to1000 p.s.i.g. no change in the yields resulted.

EXAMPLE III The use of some sulfur compounds as catalyst is ilmade using1 mole percent iodine as the catalyst. The lustrated by the resultsshown in Table III. The presisopropylbenzene and iodine were charged toa pressure sure was 500 p.s.i.g.

Table III n-propyl- Catalyst Mole, Temp., Time, Conv., Se1ect., benzene,

Percent 0. min. Percent Percent moles/100 moles feed (C li-,8); 1 500 5.0 1.8 1. 2 5.0 500 5.0 20.2 64.0 12.0 5. 525 10. 0 18.7 33. 7 0. a 1

2 5 500 11.1 10.3 63.1 12.2 2: 0 600 10. a as. 1 70. 5 23. a

EXAMPLE IV bomb from which they were continuously fed at a desired ratethrough a reaction tube under a pressure of 500 p.s.i.g. Thetemperatures, contact times, conversions and selectivities are shown inthe following Table I.

ache-93c 9 All of the above runs shown in Examples I through IV weremade by continuously passing the hydrocarbon and catalyst through theunpacked reaction zone, as mentioned. The runs shown in the nextfollowing Table V were carried out batchwise in an autoclave.

10 350 C. and about 525 C. for a time between about /2 minute and 5hours suflicicnt to effect substantial cata lytic isomerization butinsufficient for the concentration of the formed isomer containing thealkyl group attached through a primary alkyl carbon atom to exceed 95%of Table V isomerized Feed Catalyst Mole, Temp., P.s.l.g. Time, Oonv.,Select., product,

percent 0. hrs. percent percent moles/100 moles feed 1. 400 500 3.0 45.075. 34. 0 1. 0 450 750 1. 0 71. 9 60. 7 43. 7 1. 0 400 500 3.0 33. 7 38.1 12. 8 1. 0 400 500 3. 0 73. 4 84. 4 62. 0 1.0 470 l, 000 1. 0 72. 515. 2 10. 7 2. 0 150 0 73.0 0 pP-cymene I2 1. 0 450 800 1. 0 78. 6 41. 032. 3 ert-butyl-benzene 1. 0 450 850 1. 0 84. 5 36. 6 30. 9 Oumene B 1.0300 110 1.0 0 Do 1. 0 450 600 1. 0 53. 3 80. 4 42. 9alpha-methyl-styre 1. 0 450 1, 100 1. 0 polymer polymer 0Isobutyl-benzenel. 0 450 600 1. 0 84. 5 6. 1 5. 2 Cumene 1. 0 450 800 1.0 50. 2 53. 5 26. 8 Do 1.0 450 1,100 1.0 80.6 35.0 27. 9 Do- 4. 0 450800 1. 0 36. 3 75.0 27. 2 Do 4.0 450 800 1. 0 54. 5 62. 4 34. 1

Regarding the results shown in Table V it will be noted that forcomparison some inoperative materials and conditions have been included.Regarding the temperatures and times noted it should be pointed out thatthe time for heating and cooling the autoclave varied somewhat. Thepressures noted are the maximum pressures attained.

For exploratory work, tests were carried out in sealed glass tubes. Thesuccess of such tests proves that the presence of metal surface is notnecessary for the catalysis of the isomerization reaction. For example,cumene was sealed with 1 mole percent (C H S) and heated at 500 C. forone hour. This resulted in 61.5% conversion with 54.3% selectivitygiving 33.4% of the desired n-propylbenzene.

It should be pointed out that in contrast to the isomerization ofalkylaromatics with Lewis acid catalysts very little, if any (ca 0.2%)disproportionation and ring migration occurred in any of the aboveexamples. For example, in the isomerization of p-cymene1-methyl-4-npropylbenzene was produced but no m-cymene orl-methyl-3-n-propylbenzene could be found by infrared analysis. Also theamount of coke formation was always very small.

In the above we have described the isomerization of alkylaromaticshaving the alkyl group attached to the aromatic through a secondary ortertiary carbon atom, i.e. a carbon atom having not more than onehydrogen atom and no double bond, and the subjoined claims are limitedto this isomerization. The question therefore naturally arises as to thereverse isomerization. The reverse isomerization does take place butonly to a very limited extent due to the relative stabilities of theisomers for which reason the control of the contact time is important asspecified above. there is no economic incentive to effect the reverseisomerization of a valuable material to one of less value.

We claim as our invention:

1. Process for the production of aromatic hydrocarbons having at leastone side group of at least three carbon atoms connected through aprimary carbon atom in an alkyl group having not more than five carbonatoms which comprises adding a catalytic amount of a freeradical-forming catalyst containing an element selected from the groupconsisting of Cl, Br, I, S, and combinations thereof, in a form selectedfrom the group consisting of the free elements, their hydrides, andsemi-labile organic -compounds thereof, to an aromatic hydrocarbonhaving at least one side group of at least three carbon atoms connectedthrough a non-primary alkyl carbon atom in an :alkyl group having notmore than five carbon atoms, maintaining the mixture at a temperaturebetween about Also of importance is the fact that the equilibriumconcentration thereof at the reaction temperature, and separating as themajor reaction product the said isomer having the alkyl group attachedthrough a primary alkyl carbon atom.

2. Process for the production of atromatic hydrocarbons having at leastone side group of at least three carbon atoms connected through aprimary carbon atom in an alkyl group having not more than five carbonatoms which comprises adding a catalytic amount of a free radicalforming catalyst containing I in a form selected from the groupconsisting of the free element, its hydrides, and semi-labile organiccompounds thereof, to an aromatic hydrocarbon having at least one sidegroup of at least three carbon atoms connected through a non-primaryalkyl carbon atom in an alkyl group having not more than five carbonatoms, and maintaining the mixture at a temperature between about 350 C.and about 525 C. for a time between about /2 minute and 5 hourssufiicient to effect substantial isomerization but insuflicient for theconcentration of the formed isomer containing the alkyl group attachedthrough a primary alkyl carbon atom to exceed of the equilibriumconcentration thereof at the reaction temperature, and separating as themajor reaction product the said isomer having the alkyl group attachedthrough a primary alkyl carbon atom.

3. Process for the production of aromatic hydrocarbons having at leastone side group of at least three carbon atoms connected through aprimary carbon atom in an alkyl group having not more than five carbonatoms which comprises adding a catalytic amount of a freeradical-forming catalyst containing bromine in a form selected from thegroup consisting of the free element, its hydrides, and semi-labileorganic compounds thereof, to an aromatic hydrocarbon having at leastone side group of at least three carbon atoms connected through anonprimary alkyl carbon atom in an alkyl group having not more than fivecarbon atoms, and maintaining the mixture at a temperature between about350 C. and about 525 C. for a time between about /2 minute and 5 hourssulficient to efiect substantial isomerization but insufficient for theconcentration of the formed isomer containing the alkyl group attachedthrough a primary alkyl carbon atom to exceed 95% of the equilibriumconcentration thereof at the reaction temperature, and separating as themajor reaction product the said isomer having the alkyl group attachedthrough a primary alkyl carbon atom.

4. Process for the production of a normal-propyl aromatic hydrocarbonwhich comprises adding a catalytic amount of a free radical-formingcatalyst containing an element selected from the group consisting of Cl,Br, I, S, and combinations thereof in a form selected from the 1 1 groupconslsting of the free elements, their hydrides, and semi-labile organiccompounds thereof, to an isopropyl aromatic hydrocarbon containing noalkyl group having more than 5 carbon atoms, maintaining the mixture ata temperature between about 350 C. and 525 C. for a time between about/2 minute and 5 hours sufiicient to effect substantial catalyticisomerization but insufficient for the concentration of thenormal-propyl isomer to exceed 95 of the equilibrium concentrationthereof at the reaction temperature, and separating as the majorreaction product said normal-propyl aromatic hydrocarbon.

5. Process for the production of an isobutyl aromatic hydrocarbon whichcomprises adding a catalytic amount of a free radical-forming catalystcontaining an element selected from the group consisting of Cl, Br, I,S, and combinations thereof in a form selected from the group consistingof the free elements their hydrides, and semilabile organic compoundsthereof, to tert-butyl aromatic hydrocarbon containing no alkyl grouphaving more than 5 carbon atoms, maintaining the mixture at atemperature between about 350 C. and 525 C. for a time between about /2minute and 5 hours sufiicient to effect substantial catalyticisomerization but insufficient for the concentration of the isobutylisomer to exceed 95% of the equilibrium concentration thereof at thereaction temperature, and separating as the major reaction product saidisobutyl aromatic hydrocarbon.

6. Process for the production of 1-methy1-4-normalpropyl-benzene whichcomprises adding a catalytic amount of a free radical-forming catalystcontaining an element selected from the group consisting of Cl, Br, I,S,

and combinations thereof in a form selected from the group consisting ofthe free elements, their hydrides, and semi-labile organic compoundsthereof, to 1-methyl-4- isopropyl-benzene, maintaining the mixture at atemperature between about 350 C. and 525 C. for a time between about /2minute and 5 hours sufiicient to efiect sub stantial catalyticisomerization but insuflicient for the concentration of the producedisomer to exceed 95% of the equilibrium concentration thereof at thereaction temperature, and separating as the major reaction product said1-methyl-4-isopropylbenzene.

7. Process for the production of 1,2-diphenylethane which comprisesadding a catalytic amount of a free radical-forming catalyst containingan element selected from the group consisting of Cl, Br, I, S, andcombinations thereof in a form selected from the group consisting of thefree elements, their hydrides, and semi-labile organic compoundsthereof, to 1,1-diphcnylethane maintaining the mixture at a temperaturebetween about 350 C. and 525 C. for a time between about /2 minute and 5hours sufiicient to efiect substantial catalytic isomeriza tion butinsufiicient for the concentration of the 1,2-isomer to exceed 95% ofthe equilibrium concentration thereof at the reaction temperature, andseparating as the major reaction product said 1,2-dipher1ylethane.

Ipatieff et al Mar. 2, 1954 Raley et al Mar. 31, 1959

1. PROCESS FOR THE PRODUCTION OF AROMATIC HYDROCARBONS HAVING AT LEASTONE SIDE GROUP OF AT LEAST THREE CARBON ATOMS CONNECTED THROUGH APRIMARY CARBON ATOM IN AN ALKYL GROUP HAVING NOT MORE THAN FIVE CARBONATOMS WHICH COMPRISES ADDING A CATALYTIC AMOUNT OF A FREERADICAL-FORMING CATALYST CONTAINING AN ELEMENT SELECTED FROM THE GROUPCONSISTING OF CL, BR, I, S, AND COMBINATIONS THEREOF, IN A FORM SELECTEDFROM THE GROUP CONSISTING OF THE FREE ELEMENTS, THEIR HYDRIDES, ANDSEMI-LABILE ORGANIC COMPOUNDS THEREOF, TO AN AROMATIC HYDROCARBON HAVINGAT LEAST ONE SIDE GROUP OF AT LEAST THREE CARBON ATOMS CONNECTED THROUGHA NON-PRIMARY ALKYL CARBON ATOM IN AN ALKYL GROUP HAVING NOT MORE THANFIVE CARBON ATOMS, MAINTAINING THE MIXTURE AT A TEMPERATURE BETWEENABOUT 350*C. AND ABOUT 525*C. FOR A TIME BETWEEN ABOUT 1/2 MINUTE AND 5HOURS SUFFICIENT TO EFFECT SUBSTANTIAL CATALYTIC ISOMERIZATION BUTINSUFFICIENT FOR THE CONCENTRATION OF THE FORMED ISOMER CONTAINING THEALKYL GROUP ATTACHED THROUGH A PRIMARY ALKYL CARBON ATOM TO EXCEED 95%OF THE EQUILIBRIUM CONCENTRATION THEREOF AT THE REACTION TEMPERATURE,AND SEPARATING AS THE MAJOR REACTION PRODUCT THE SAID ISOMER HAVING THEALKYL GROUP ATTACHED THROUGH A PRIMARY ALKYL CARBON ATOM.